A process for producing phenol and/or cyclohexanone is described in which cyclohexylbenzene is contacted with an oxygen-containing gas under conditions effective to produce an oxidation effluent comprising cyclohexylbenzene hydroperoxide and at least part of cyclohexylbenzene hydroperoxide is contacted with a cleavage catalyst under conditions effective to produce a cleavage effluent containing phenol and cyclohexanone. At least one of the oxidation effluent and the cleavage effluent contains at least one phenylcyclohexanol as a by-product and the process further comprises contacting the phenylcyclohexanol with a dehydration catalyst comprising a molecular sieve of the MCM-22 family under conditions effective to convert at least part of the phenylcyclohexanol to phenylcyclohexene.